Data receiving circuit



April 5, 1966 D. F. BURDETT ETAL 3,245,040

DATA RECEIVING CIRCUIT Filed April 2l, 1958 NNJ S5.. w f

D. E BURDETT J. R. DA VEY .4.71 HARTV U 2%: gs' j l/V VEN TORS B By OSTENDOREJ ATTORNEY United States Patent O 3,245,040 DATA RECEIVING CIRCUIT David F. Burdett, Gleniidge, lJamesR. lDavey,f Franklin Township, Somerset County, and Austin T. Harty, Whippany, NJ., and Bernard stendorf,;lr., Stamford, Conn., -assignors to Bell Telephone "Laboratorien-Incorporated, New York, N.Y.,ra corporation Iof Newy York lFiled A111121, .1958,Ser.'-No. 729,717 3 Claims. '(Cl. 340-1725) This invention relates in .general to .communication systems and more `particularly. to rcontrol arrangements for such systems.

High 4speed digital communication :and vdata systems are lwidely .acceptedibecause of Vt-heir .extremely favorable vtransmission and resolution characteristics `and such systems are `further enhanced through fthe iuseof time division multiplexing to achieve leconomies lin transmission media. Such systems, however, are rnot without special problems, an example lacing the 1problem of accurate timingin the :handling :of digital `data lboth in transmitting and receiving arrangements.

Heretofore, iin Isuch systems,the timing and counting function-ings have been divorced from `ther data circuits, and this has resulted in a less than `optimum use of circuitry and undue circuit complexity.

Accordingly, it is an object of this invention -to reduce the complexity of digital data systems.

It is `another object of this invention -to combine functions in system elements to `etfectLsa-vings inequipment.

Itis a further object of `this invention to more efficiently perform timing `andcounting Afunctions in such systems.

It is still another o'bject'of this invention-to increase the .iiexibility of timing )and counting circuits `employed in digital data systems.

Yet another'object of the :present -invention is ytomore efficiently perform timing, counting and data checking h functions in digital systems.

These and other objects of .this invention -are achieved -in one specific illustrative emlbodiment whereiniboth -sys- =temtirning and data ystorage are performed in a single shift rregister. In the case yof a-data receiver, the shift register and other elements of the system are recycled just preceding the initiation olf a message land in the recycling operation the shift register is set to a discrete initial pattern. The discrete initial pattern ymay in the simplest instance, be a l stored in the lirst stage ofthe shift register and "(ls storedin the remaining stages ofthe register or any other discrete pattern which can lbe readily recognized.

'As data is serially shifted into the receiving shift register,

the initial "1, stored in the first stage,'proceeds through the succeeding stages of the register. Circuit lelements responsive to the setting of `a shift register stage to the l state recognize the Vprogress of t-he initial 1through the register and, in accordance Iwith the progress of the initial 1, provide timing or counting 4pulses to perform Work operations such ,as to order :agparitycheck or address recognition, or provide an indication thatan entire message has been received. Accordingly, both data storage and timing or counting 'functions are lachieved -in `a common shift register.

In accordance with onefeature of Athis invention, 1a

-shift register, having 'a suliicient number of stages to store a complete message, or'aseparablesection thereof, is em- 'ployed both `as -a data storage vdevice and as a timing Vor fcounting `device and, in addition, is comibined With-circuitry Ifor checking the parity of the message.

In-accordance with lanother feature of this invention,.a

`parity check of the message is .accomplished lby means of ya'single binary counter connected to the first stage of a receiving shift register in conjunction with signals derived ice 'from passage of a discrete initial pattern throughthe shift register.

In accordance -with still another feature rof this 'invention, information is transferred from theshift register to :data iutilization circuits Yonly upon the `occurrence of parity Awithin the message .and completion of the message.

The above and Yother r[objects `andifeatures of this in- Mention will be Vfully lunderstood 'when read vwith reference to `thezsingle :ligure :drawing "which shows a dat-a receiver advantageously .employing the teachings of this invention.

'llhe circuitshown inthe 'drawing is arranged Atio-.accept a binary :message comprising two Vten bitrvvords. The message -originates 1in the :data source A2 andis inserial digital ldata form. `='I`he message is predetermined to halve even vparity in each of the words, that is, :an `even .numlber of "1s in each yof the ten 'bitlwords riFailure yof parity in either word vinitiates an alarm signal :and :prevents transffer of data ifrom theshiftregister -1 -to the data utilization circuit 12.

'-In the drawing, there is shown1a data source 2 which provides a -recycle lsignal on conductor4l, a start signal Yonconductor 42, anddata-signals onconductor 43. The

fsliift register '-1 has input, output, advance, land recycle terminals. The data source data conductor 43 is connected fto the shift regi-ster input` terminal 25. The data signal recycle yconductor 41 is vconnected to the recycle pulse'source v4 Which-provides a'recycle pulse on con- "ductor 15 undercontrol lof a signal'on conductor41. The yenergization of recycle conductor establishes the proper initial conditions inthe 'shift iregister 1 and prepares the attendant circuitry for receipt of a data message. The advance pulse source isset in step by a signal from the datasource fon conductor=42- The bistable circuits 6 and '7 are connected to the 1 output terminals'ofthe eleventh and twenty-iirst stages of the shift register, andvare set lto their 1state when theirfrespective shift register stages havebeen set. The binary counter'S lvis arranged to count the settings vof the first stagerofthe shift register and isa-rlranged to beset to its initial condition upon energization of the recycle 'pulse Vsource 4. The alarm flip-dop 14 is arranged to lbe lset to its 1 state lupon the failure of parity in either of the received words, and the output AND gates represented by'gatessll, 31, and "32 vare energizedwhenever parity occurs in both Words of the message Vand `upon completion of the message. Energization of the output AND gates such as 30, 31, and 32 effects trans- -fer of the -information in the shift register to the .data utilization circuit 12. The data utilization circuitlZ may consist of circuitry for further processing the message data `Or may advantageously consist of additional storage or display arrangements.

I ust preceding the transmission of data over conductor 43, recycle pulse source 4 is energized by a start signal from the'datafsource `2 over Conductor 41. Energization `of the-recycle pulse-source 4 provides an output signal on conductor 15 which is effective to set the first stage of the shift register; reset all remaining stages of the shift regductor 15. Accordingly, the shift register 1 is cleared of all priordata and the initial patternconsisting of a"1 in the first stage and a "0inleach of the remaining stages Vis established. yImmediately after or coincident with the recycling of the shift register and its attendant'logic circuitry, the advance pulse source is set in phase by a signal from the data source 2 over conductorr42. Ac-

cordingly, the shift register advance pulses over conductors 26 and 27 are arranged to occur at the center of the pulses from the data source 2 over conductor 43. The serial digital message follows and is shifted into the shift register. Each time the first stage of the shift register is set to its 1 state as the message data is shifted into 4the shift register, a signal is applied through gate 18 and condenser 17 to operate binary counter 5. The initial 1 Vwhich is set in the rst stage at the time the circuit was recycled precedes the message data in the shift register,

and when the eleventh stage has been set indicating the and 7 will not be energized until shortly after setting of the binary counter 5 has been completed.

As the data was shifted into the register, the binary counter 5 was advanced one count each time a l was shifted into the first stage. Accordingly, if even parity,

that is an even number of ls,"J is present in the first ten bitsof the serial message, the binarycounter will have been set and reset an even plurality of times so that it is in its 1 state when the initial 1 reaches the eleventh stage. Y

The setting of the flip-flop 6 to its 1 state applies a signal through the condenser 9 and OR gate 8,to conductor 20. This signal is combined with the 0 output signal on conductor 19 from binary counter 5. If the binary counter is in its 0 state at the time the signal caused by the setting of flip-flop 6 to its 1 state occurs, failure of parity is indicated and the alarm flip-flop 14 is set to its 1 state through the enablernent of AND gate 13 and the accompanying energization of conductor 21. With alarm Hip-flop 14 set to its 1 state, alarm signal 51 will be operated by a signal over the 1 output conductor 52 from alarm flip-flop 14. After operation, alarm flip-flop 14 is reset by the manual operation of alarm reset switch 50 which applies a potential to the reset lead of alarm ip-op 14. If parity is present in the ten bits, the binary counter 5 will be in its l state and the alarm AND gate 13 will not be enabled, accordingly, ala-rm flip-flop 14 will remain in its 0 state and alarm -signal 51 will not be operated.

As the remainder of the message, that is, the next ten bit word of the message, is shifted into the shift register,

the initial l proceeds until it reaches the twenty-first stage. It should be noted that only the set terminal of the flip-flop 6 is connected to the shift register output terminal, therefore, subsequent transfer of ls and Os to the leleventh stage of the shift register will not affect the state of the ip-op 6.

Transfer of the initial 1 to the twenty-first stage will set flip-flop 7 which is connected to the output termi-Y nal of the twenty-first stage. The signal derived from the setting vof flip-Hop 7 is transmitted through condenser 10,

`OR gate 8, and conductor 20 to the AND gate 13,. If as in -the previously vdescribed instance, the binary counter is in its 1 state, indicating presence of parity in the word just checked, the alarm AND gate 13 will not be enabled. When the 1 output conductor 46 of the last stage of vthe shift register has been energized by the transfer of the initial 1 thereto, the advance pulse source 3 will be inhibited thereby preventing further transfer of inforymation through the shift register.

When the initial "1 is shifted into the twenty-firstA stage, indicating the receipt of -a complete message, the information stored in the rst twenty stages of the shift register will be transferred to t-he data utilization circuit l12 if parity is present. Transfer is accomplished through the output AND gates represented by 30, 31, and 32.

The D.C. state of the output conductor of the flip-flop 7 is used as a tirst enabling signal tothe output AND gates last stage of the register.

such as 30, 31, and 32. The 0 output conductor of the alarm dip-flop is a second enabling lead to the AND gates 30, 31, and 32. If the alarm flip-flop is in its 0" state, indicating presence of parity, when the ip-ilop 7 is set to its 1 state, indicating completion of .a message, the output AND gates 30, 31, and 32 will he enabled t0 transfer the information stored in the lirst twenty stages of shift register '1 to data utilization circuit 12.

If parity has failed in leither of the ten bit words of the message, the alarm flip-flop will have been set to its l state, thereby inhibiting AND gates 30 through 32 vand thereby preventing transfer of the message to utilization circuit 12-when the initial l is shifted into the twenty-first stage of shift 'register 1.

The above arrangements are but one specific illustrative embodiment of an arrangement whe-rein ythe teachings of this invention areadvantageously employed. It will be readily .recognized -that numerous other arrangements embodying the concepts of` this invention may be devised Vby those skilled-in the art Without departing from the vspirit and scope of the invention. For example, if it is desired, -a more-secure pattern consisting of other than Yan initiallfmay be employed. Further, the work operations timed through the progress of the initial l 'being shifted down -the shift register are not limited to parity checkingand transfer of the information to the 'data utilization circuit, but rather may include any of the lor other logical operations with regard to data. Further,

the teachings of this invention are not limited to the receiving arrangements shown herein, but rather may be advantageously employed in transmitting arrangements as well. For example, Ia discrete initial pattern may be inserted in a transmitting shift register along with vmessage data'that is to be transmitted serially. For example, Aa l may be inserted in the last stage of the register and another 1 inserted in a stage some number of stages away from the last stage. By way of example, a l may be inserted in the last stage and in the fth from the If it is established as a rule that only message dat-a codes which have a l in at least every fourth bit are employed, it is possible to monitor the ve stages closest to the transmitting end of the shift register and thereby determine when the last bit of the message has been transmitted. Accordingly, as the last bit of information is shifted out of the register,

Ythe transmitter may be shut down. In the case of a long message, this obviously saves a great deal of equipment -since without the use of a discrete pattern accompanying -the message data, it would be necessary to provide either a separate counting chain or to monitor all of the stages l'of the transmitting shift register.

It is noted that a sole divisional application Serial No.

Y 166,133, filed Jan. 15, 1962, in the name of B. Ostendorf, Jr., is directed to certain aspects of the subject matter disclosed but not claimed herein.

What is claimed is: 1. In a communication system the combination comprising a plural stage shift vregister having input, advance and recycle terminals, each of said stages having an output terminal, a message data source connected nto ysaid shift register input terminal, recycle pulse source connected to said recycle terminals -and under con- 'trol of said data source for establishing a discrete initial pattern of electrical states of said stages of said shift to the output terminal of the rst stage of said shift register, bistable circuit means connected to the output terminals of certain of said shift register stages, gating means responsive to said binary counting means and said bistable circuit means for checking parity in said message and alarm means responsive to said gating means fo-r indicating failure of parity in said message.

2. In a communication system the combination comprising a data utilization circuit, a plural stage shift register having input, output, advance and recycle terminals, a message data source connected Ito said shift register input terminal, an advance pulse source connected to said shift register advance terminals, binary counting means having input and recycle terminals, said counting means input terminal connected to the output terminal of the rst stage of said shift register, Ibistable circuit means having input and recycle terminals, said input terminal of said bistable means connected to the output terminal of another of said shift register stages for indicating the position of the message in said shift register, recycle means connected to said recycle terminals of said shift register, said binary counting means and said bistable means, an alarm circuit to indicate parity failure, first switching means responsive to said binary counter state and the state of said bistable circuit to enable said alarm means upon failure of parity in said message, and second switching means connected between said shift register output terminals and said data utilization circuit and controlled by said alarm means and said lbistalrle circuit means -to eifect transfer of inform-ation from said shift register to said data utilization circuit.

v3. In a communication switching system the combination comprising a plural stage shift register having input, advance and recycle terminals, each of said stages having an output terminal, a serial data message source connected .to said input terminal, an advance pulse source connected to the advance terminals of said shift register and under control of said data source, a recycle pulse source connected to the recycle terminals of said shift register for establish-ing a discrete initial pattern of electrical states of said shift register stages, binary counting means connected to the output terminal of the first stage of said shift register, gating means interposed between said rst stage output terminal and said binary counting means, said gating means inhibited by a signal from said recycle pulse source, bistable circuit means connected to the output terminals of certain of said stages of said shift register, delay means interposed between said output terminals of said cert-ain stages of said shift register and said -bistable circuit means, the reset terminals of said bistable circuit means being connected -to said recycle pulse source, gating means connected to the output terminal of said binary counting means and the output terminals of said bistable means for checking parity in said message, bistable alarm means responsive to the output of said gating means, said bistable alarm means set to the 1 state upon failure of parity in said message, a data utilization circuit; and a plurality of gate means under joint control of said alarm bistable means and one of said bistable means connected to said certain output terminals for gating the message in said shift register in parallel to said data utilization circuit.

References Cited by the Examiner UNITED STATES PATENTS STEPHEN W. CAPELLI, MALCOLM A. MORRI- SON, FREDERICK M. STRADER, Examiners. 

1. IN A COMMUNICATION SYSTEM T COMBINATION COMPRISING A PLURAL SHIFT REGISTER HAVING INPUT, ADVANCE AND RECYCLE TERMINALS, EACH OF SAID STAGES HAVING AN OUTPUT TERMINAL, A MEASSAGE DATA SOURCE CONNECTED TO SAID SHIFT REGISTER INPUT TERMINAL, RECYCLE PULSE SOURCE CONNECTED TO SAID RECYCLE TERMINALS AND UNDER CONTROL OF SAID DATA SOURCE FOR ESTABLISHING A DISCRETE INITIAL PATTERN OF ELECTRICAL STATES OF SAID STAGES TO SAID SHIFT REGISTER, SAID RECYCLE PULSE SOURCE EFFECTIVE TO SET THE FIRST STAGE OF SAID SHIFT REGISTER TO THE "1" STATE AND TO RESET ALL OTHER STAGES OF SAID SHIFT REGISTER TO THE "0" STATE, AN AD- 